The amount depends in the indication of treatment. A Lip filler may demand a different number of vials, depending on your features and desires.
For a full facial contouring we can use up to several vials.
Remember, 1 vial contains 2 pea sizes of hyaluronic acid. It takes around 15 vials to fill up a soup spoon.
Subtle changes can use small quantities, but to change facial feature you might need more.
The average duration of hyaluronic acid is 9-12 months. Some of them can last up to 3 years, especially in the tear through areas. Hyaluronic acid also helps to create more collagen, so repeated applications can also lead to a natural rejuvenation of the skin.